In the manufacture of integrated circuits, a flip-chip connection is often used to attach an integrated circuit die (IC die) to a carrier substrate, such as an integrated circuit package (IC package) or a motherboard. A flip-chip configuration uses an array of metal bumps that are arranged on the surface of the IC die. The metal bumps are aligned with corresponding solder balls on the IC package. Once aligned, an annealing process is carried out at a temperature above the melting point of the solder to cause the solder balls to reflow and wet the surface of the metal bumps. The solder balls and metal bumps are then rapidly cooled to minimize the intermixing of metals. Spaces between and around the metal bump/solder ball connections are filled with an underfill material, such as an epoxy resin.
A critical issue that is challenging the whole microelectronics industry is the cracking and delamination of relatively weak low-k interlayer dielectric (ILD) layers within the IC die which occur during the flip-chip packaging process. With current designs, the load upon the ILD layers within the IC die is high due to shear stresses from thermal expansion mismatches and normal stresses due to die and package warping behavior. Historically, ILD cracking and delamination has not been an issue in the industry because silicon dioxide, a relatively strong dielectric material, has been typically used for the ILD layers. But because the use of relatively weak low-k dielectric materials is becoming standard in the industry, improved designs are needed to reduce the cracking and delamination of ILD layers containing these low-k materials. Furthermore, as the dimensions of integrated circuit dies and packages continue to scale down, these problems are expected to become increasingly troublesome because of the trend towards reduced bump pitches and reduced bump diameters.